1. Field of the Invention
The present invention relates generally to a temperature sensor; and more specifically, to a coolant temperature sensor that monitors the temperature of a cooling fluid used with an internal combustion engine.
2. Description of Related Art
Currently, automotive vehicles use an internal combustion engine as a power plant for the vehicle. Internal combustion engines generate friction, which correspondingly generates heat. To dissipate the heat and maintain proper engine temperature, many automotive vehicles utilize a liquid cooling system. The liquid cooling system operates by circulating coolant through the engine to collect the heat and then through a radiator to dissipate it. One component of the cooling system includes a cool and temperature sensor that provides coolant temperature feedback or information to the vehicle operator. In addition, the temperature sensor also provides information to the vehicle control module, which operates the cooling fans and other engine operating parameters based on the temperature sensor signal.
An automotive engine cooling system is a harsh environment due to the corrosive behavior of the fluids used and the temperature extremes. A temperature sensor must be able to survive the operating conditions, accurately detecting temperature, respond quickly to temperature changes, maintain a liquid tight seal and have a long life.
Traditional coolant temperature sensors typically include a variable resistor type sensor or often referred to as a thermistor. The sensor is positioned in a two-piece housing having a brass component that is either machined or stamped and a separately molded plastic connector component. The plastic connector component is connected to the brass component using various methods. Typically, a gasket seals the interface or joint between the brass component and the plastic connector component. After assembly of the housing, the sensor is typically inserted into the housing and secured in place.
In addition, U.S. Pat. No. 5,844,135 illustrates a coolant temperature sensor using a two-piece plastic assembly. The temperature sensor includes an integrally formed plastic body including a sensor part and an adjoining plug part. A housing of temperature resistant plastic is directly injection molded over and surrounds the sensor part 19.